In addition to their small arms,
infantry were equipped with
grenades. These were small bombs
with
a 3- to 5-second fuse and were designed to be thrown by hand or fired
from a rifle using a special blank cartridge.
Hand grenades could be either offensive or defensive. Defensive grenades, such as the American "pineapple," had a heavy metal case designed to break into deadly fragments when the grenade detonated. The lethal radius was greater than the distance the average soldier could throw the grenade, so the thrower had to take cover to avoid being wounded by his own grenade. Offensive grenades had no heavy metal case to produce fragments and relied purely on the blast of the high explosive for their effect. This meant they had a much smaller lethal radius and the thrower did not have to take cover after throwing the grenade. Many offensive grenades could be converted into a defensive grenade using a metal jacket, but these seem not to have seen much use.
In addition to high explosive grenades, the infantry were equipped with smoke grenades to provide cover for movement or to mark enemy positions to heavy weapons or ground support aircraft. Those based on white phosphorus also had some incendiary and antipersonnel capability. There were also incendiary grenades filled with thermite, a mixture of aluminum and iron oxide that burned hotly enough to melt steel. These were used mainly for demolition work.
The standard Japanese grenades
were the Type 91 and Type 97 grenades. The Type 91 had a 7.5-second
fuse and adapters to allow it to be used either as a rifle grenade or
as a projectile for the Type 89 "knee mortar."
Both were filled with two ounces (57 grams) of TNT. The Type 97 had a
4.5 second fuse and was used only as a hand grenade. Both broke into
very small
fragments that were less lethal and had a much smaller kill radius than
the corresponding Allied
grenades. The fuse was rather unusual, being
lit by banging the grenade on any solid surface to drive a firing pin
into an igniter. The fuse was also unreliable if stored for any length
of time, tending to go off too quickly.
The Japanese apparently planned to replace these rather dangerous and ineffective grenades with a model that used a friction igniter. However, few of these grenades were ever manufactured and their effectiveness is unknown.
The Japanese also employed a stick grenade resembling the German "potato-masher," which used a 4.5-second friction fuse and was filled with three ounces (85 grams) of picric acid. This was declared obsolete before war broke out, but existing stocks were used throughout the war in spite of erratic fuses that sometimes detonated the grenade almost immediately.
The standard U.S. grenade was the M11A1 fragmentation grenade, a
defensive grenade filled with 0.75 ounces (21 grams) of gunpowder. This
seemingly weak fill was actually quite effective, since the slower
explosion improved the fragmentation. Because no detonator was
required, the fuse design was simple. An adapter was also supplied that
allowed the M11A1 to be used as a rifle grenade. Unfortunately,
grenades stockpiled before the war were notoriously unreliable, often
failing to go off.
The Mark 111A2 was an offensive grenade consisting of a fairly large charge of TNT (6.25 ounces or 177 grams) in a cardboard cylinder with a 4.5-second fuse. Though supposedly intended primarily for demolition work, the grenade saw extensive use for clearing houses and bunkers in the South Pacific.
The M9 anti-tank rifle grenade had a four ounce (113 gram) shaped charge that could penetrate 40mm of armor. It was very quickly replaced by the M9A1, which moved the fuse from the nose to the rear of the grenade where it would not interfere with the jet, improving the penetration to 60mm. This was enough to penetrate the rather thin armor on most Japanese tanks. However, the grenade seems to have seen little use, perhaps because of the superiority of the bazooka in the antitank role.
The M15 was a white phosphorus grenade with a 4.5-second fuse. On
detonation, it scattered the phosphorus over a radius of 25 yards (23
meters.) It was widely employed as an anti-personnel grenade in the
Pacific. The M8 used hexachloroethane to produce white smoke, while the
M16 and M18 produced colored smoke for target designation. The M8
smoked for three minutes, the M16 for 2 minutes 15 seconds, and the M18
for one minute.
The M14 was a thermite grenade used to burn out strong points or demolish equipment.
The standard British
grenade was the Number 36M Mills grenade, a defensive grenade which was
filled with 2.5 ounces (71 grams) of Baratol. By the time of the
Pacific War, the original 7-second fuse had been replaced with a
4-second fuse. Because the detonator was not centered in the grenade,
the explosion was asymmetric and fragmentation was erratic. Large
fragments could be thrown up to 100 yards, making it vital for the
thrower to take cover. However, the grenade was powerful and very
reliable. Various attempts to improve the design failed, and the
grenade remained in use for decades after the war ended. It could be
fitted with a tail rod for use as a rifle grenade, and this version
retained the 7-second fuse.
The Number 68 antitank rifle grenade was filled with 5.5 ounces (156 grams) of explosive and exploded on impact. It was the first shaped-charge antitank weapon to enter service with any nation, and it was capable of penetrating 50mm of armor. However, it is unclear whether this grenade was issued to forces fighting against the Japanese. At one point a rather strange suggestion was made to fire the grenade from a crossbow for stealth (The King's Own Wookiee Grenadiers?) This idea was quickly dropped.
The British offensive grenade was the Type 69, which with 3.25 ounces (92 grams) of explosive in a plastic case was not expected to kill so much as to shock. However, it was far from nonlethal, and there were a number of serious training accidents before this point was driven home. The grenade used an "all-ways" impact fuse that was primed when a weight pulled the pin after the grenade was pulled. This fuse contained a lead ball which, once it was armed, would detonate the grenade any way it landed. A cast iron jacket was issued to convert the grenade to a defensive grenade if needed, but this was sufficiently clumsy and inferior to a real defensive grenade that it was seldom used.
Early in 1945, 14 Army in Burma was equipped with small numbers of the experimental Number 70 grenade. This was an attempt to improve on the Mills grenade by improving the fragmentation and using an "all-ways" impact fuse. The fuse proved unreliable and the troops preferred the familiar Mills.
The Number 80 grenade contained 11.25 ounce (319 gram) white
phosphorus and had a 2.5- to 4-second fuse. Its small explosive charge
dispersed the phosphorus over a radius of about ten yards (nine meters)
to produce an instant smoke screen. It also had some value as an
incendiary and antipersonnel grenade.
The Number 85 antitank rifle grenade had a 4.25 ounce (120 gram)
shaped charge and was similar to the U.S. M9A1 rifle grenade. It saw
use only in the closing stages of the war in the Far East.
A number of other specialized grenades, some of which were downright
odd (such as the Number 74 sticky bomb and the Number 82 gammon
grenade), were also part of the British arsenal. The sticky bomb was an
explosive charge with a sticky treacle coating that allowed it to stick
to the deck of an enemy tank. Some sticky bombs were
shipped to New Guinea, where
they proved useless because the treacle
coating rapidly became moldy. It is unlikely that
any of the others saw much use in the Far East.
References
The Pacific War Online Encyclopedia (c) 2007-2008 by Kent G. Budge. Index